In the development of pulses power technology for driving multi-megavolt devices, diagnostics are required where differential voltages must be monitored at locations which may be at high voltage relative to ground. Additional problems arise when these high voltages are developed in a short time frame which causes abrupt high frequency changes in the electric and magnetic fields (RF noise). For example it is sometimes desired to monitor the voltage on the last capacitor in a many stages marx bank to determine when the marx is fully charged and ready for erection to a very high voltage. In such a case the voltage measuring device must monitor the voltage on the last capacitor to a sufficient degree of accuracy during charging; and upon erection of the marx to its high output voltage, this voltage monitoring device must be isolated from ground. Also, it must be immune to damage by suddenly changing fields within the marx. This implies that a power supply must be contained in the monitoring device which has sufficient stored energy for long time operation.
Conventional voltage measuring devices such as resistive and capacitive voltage dividers cannot be readily used for this purpose because of the high voltage breakdown problems which develop when this voltage suddenly rises to the multimegavolt level. The acoustic waveguide voltage monitor disclosed here is not vulnerable to the above problems in that the necessary electrical isolation is obtained by the acoustic waveguide, and the protection from high frequency fields is accomplished by use of a suitably designed Faraday shielded case work and filtering and clamping techniques on the differential voltage monitoring lines. The necessary electrical isolation is obtained by the use of the acoustic waveguide and is much cheaper, less fragile, and suitable tubing may already be inherent in the system. Many such systems require pressurization of internal components by insulating gas, and the supply tubing is by necessity of sufficient voltage isolation so that it might be used as an acoustic waveguide.